x86/alternative: Support relocations in alternatives

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A little while ago someone (Kirill) ran into the whole 'alternatives don't
do relocations nonsense' again and I got annoyed enough to actually look
at the code.

Since the whole alternative machinery already fully decodes the
instructions it is simple enough to adjust immediates and displacement
when needed. Specifically, the immediates for IP modifying instructions
(JMP, CALL, Jcc) and the displacement for RIP-relative instructions.

  [ bp: Massage comment some more and get rid of third loop in
    apply_relocation(). ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230208171431.313857925@infradead.org

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This commit is contained in:

Peter Zijlstra 2023-02-08 18:10:52 +01:00 • committed by Borislav Petkov (AMD)

parent 6becb5026b

commit 270a69c448

2 changed files with 173 additions and 96 deletions

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261

arch/x86/kernel/alternative.c

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8

tools/objtool/arch/x86/special.c

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